In a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) wireless communication system or network, such as an IEEE 802.11 wireless local area network, co-channel frame collisions are inevitable. To maximize throughput, the receiver of a wireless device (e.g., an access point or a client device) needs to successfully decode one of the frames in the collision.
There are techniques to maximize the probability of successfully decoding one of the frames involved in the collision. One technique is referred to as “stomp-and-restart” in which if, after a receiver has acquired a frame (start-of-packet or “SOP”) and begins decoding the data, a subsequent stronger frame is received. The receiver will abort decoding the first frame and re-acquire on the second frame. If the signal strength of the second frame is much larger than that of the first frame, the second frame is likely to be successfully decoded. It is possible that the second frame is not substantially stronger than the first frame, in which case both frames are lost.
Conventional stomp-and-restart mechanisms assume collocated receiver paths (e.g., multiple-input multiple-output (MIMO)) are impacted in roughly the same way by the colliding packet; that is, all collocated receiver paths are subject to the same wideband shadow fading (one antenna is not blocked by a wall while the other antennas see a clear line-of-sight) and roughly the same path-loss (receive signal strength variations across antennas exists, but are relatively small for collocated antennas). Here, “collocated” refers to antennas spaced on the order of a wavelength, and remote receiver devices (each comprising a plurality of antennas) are spaced on the order of ten or a hundred or a thousand wavelengths.